CA2188332A1 - Drilling assembly for drilling holes in subsurface formations - Google Patents
Drilling assembly for drilling holes in subsurface formationsInfo
- Publication number
- CA2188332A1 CA2188332A1 CA002188332A CA2188332A CA2188332A1 CA 2188332 A1 CA2188332 A1 CA 2188332A1 CA 002188332 A CA002188332 A CA 002188332A CA 2188332 A CA2188332 A CA 2188332A CA 2188332 A1 CA2188332 A1 CA 2188332A1
- Authority
- CA
- Canada
- Prior art keywords
- drive unit
- drill bit
- housing
- unit
- bias
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
- E21B7/06—Deflecting the direction of boreholes
- E21B7/068—Deflecting the direction of boreholes drilled by a down-hole drilling motor
Abstract
A drilling assembly for drilling holes in subsurface formations comprises a drill bit, a drive unit including a housing and a rotor operatively coupled to the drill bit to rotate the drill bit relative to the housing, and a modulated bias unit coupled to rotate with the drive unit housing and apply a lateral bias thereto in synchronism with rotation of the housing. The modulated bias unit comprises one or more hydraulic actuators including members which, in use, bear against the sides of the borehole, and means for modulating the pressure of fluid supplied to the actuators in synchronism with rotation of a component of the drilling assembly, and in selected angular phase relation thereto, whereby each hydraulic actuator is actuated in a selected rotational position of the component.
Description
"A drilling assembly for drilling holes in subsurface formations"
BACKGROUND TO THE INVENTION
The invention relates to drilling assemblies for connection to a drill string for drilling holes in subsurface formations.
S As is well Icnown, in rotary drilling rotation is imparted to the drill bit by rotating from the surface a drill string to the lower end of which the drilling assembly is coupled.
The drill bit may be controlled to drill in a required directionl for example as described in British Patent Sp~-;~;f~ion No. 2259316, by cOurli~ to the drill bit a modulated bias unit which applies a lateral disp!~.cçm~nt to the drill bit in a con~t~nt direction as the bit rotates. The modulated bias unit comprises one or more hydraulic actuators the supply of fluid under plessure to which is modulated in synch~onis--~ with rotation of the unit and bit, and in selected angular phase relation thereto, the phase relation determining the direction of the bias and hence the direction in which the bit is steered.
In motor drilling the drill bit is rotated by a downhole drive unit, such as a positive disp!~ment motor or turbine. For the purposes of steering the drill bit, the drive unit may be a steerable motor having a bent housing or offset stabilizer, or the drive unit may be connected to the drill string by a device known as a bent sub, so that the bit axis is inclined to the axis of the lower end of the drill string. During unsteered drilling the drill string and drive unit are rotated so as to negate the effect of the bend, 20 and when steering is required this rotation is stopped with the inclin~tion of the bend pGillliilg in the direction in which the drill bit requires to be steered. While steering, the orientation of the bend (or offset stabilizer), referred to as the "tool-face" angle, is 21 ~8332 monitored by a directional MWD system and controlled from the surface, initially by setting the orientation of the rotary table (then stationary). The tool-face angle is also influenced, through torsional strain, by torque in the drill string. Torque is dependent on weight on bit, and short term changes in measured tool-face angle are corrected by S adjusting weight on bit. Tool-face angle and weight on bit are influenced by torque and drag due to friction between the drill string and the side of the hole. This influence makes steering difficult in long reach holes having high inclination in which much of the string weight is supported on the lower side of the hole. The extra length of the string adds to its angular and linear co...~ r~, further increasing the influences of torque and 10 drag. These difficulties are partly overcome by using extra care and by drilling slowly to minimise distulbances due to torque at the bit. Despite this, torque and drag effects do set a limit of reach beyond which steering by o~ ing becomes impracticable. These difficulties do not apply during unsteered drilling because the drill string is rotated contin-lo..~ly reducing drag and its effect on weight on bit, and also because there is then 15 no need to control tool-face angle. Thus the loss of pent~ lion rate while steering to make directional corrections increases as lateral reach is increased.
The present invention provides a downhole drilling assembly where the drill bit is rotated by a downhole drive unit, but where steering may be effected without the neces~ity of ceasing rotation of the drill string.
Acco-ding to the invention there is provided a drilling as~lllbly for drilling holes in subsurface formations, co~ lis;ng a drill bit, a drive unit in~ dir~ a housing and a rotor operatively coupled to the drill bit to rotate the drill bit relative to the housing, and a modulated bias unit coupled to rotate with the drive unit housing and apply a lateral bias thereto in s~..cllrol~ism with rotation of the housing.
The modulated bias unit may co~ -;se one or more actuators including members S which, in use, may bear against the sides of the borehole, and means for modul~ting the force and/or motion ofthe actuators in sy..cl--~l~is-ll with rotation of a component of the drilling asse..lbly, and in s~lected angular phase relation thereto, whereby the, or each, actuator is actuated over a selected rotational range of said component.
The actuators ofthe modulated bias unit may comprise hydraulic actuators, said 10 means for modulating the force and/or motion ofthe actuators comprising means for modul~ting the pressure and/or volume of fluid supplied to the actuators.
~ nple,s of hydraulic and non-hydraulic mod~ ted bias units are described in British Patent No. 2259316 and U.S. Patents Nos. 5113953 and 3743034.
The drive unit may include fulcrum means which, in use, engage the walls of the 15 borehole being drilled, the fulcrum means being located b~lweell the modulated bias unit and the drill bit whereby the lateral bias applied by the modulated bias unit causes the drive unit to pivot about the fulcrum means so as to apply to the drill bit a lateral bias in the opposite direction to the bias applied to the drive unit by the bias unit.
Alternatively, the actu~tors of the modulated bias unit may be located adjacent 20 the drill bit so as to apply a lateral bias to the drill bit in the same direction as the lateral bias applied to the drive unit.
These last-.~ ;ol1ed ~.i.. ~.. ~1~ thus permit steering ofthe drill bit while the drill string is rotating, reducing drag and avoiding the need to control motor orientation or tool-face angle by frequent monilo~i..g and ~rlj~ from the surface. Penetration rates may therefore be ...~ Ai~ed even while steering is taking place.
All;.n~...~ in ~ccor~&~ce with the invention may be used with any downhole 5 drilling asscllll~ly where the drill bit is rotated by a downhole drive unit and, in particular, it may employed in arrangcnlellls accordi,~ to our co-pending Application No.
where the drill bit and the drive unit which rotates it are counter-l oLali,~g so as to reduce the net reaction torque l, ~ ~1ed to the drill string, as well as providing other benefits as ~cr~, I cd to in that application.
Accordingly, in a drilling asse... ,bly, incorporating a modulated bias unit, in accordance with the present invention, the drill bit may carry cutters located and orientated to pc,~o.... cutting action on the formation as the drill bit rotates anti-clockwise relative thereto, the rotor of the drive unit being operatively coupled to the drill bit to rotate the drill bit anti-clockwise relative to the housing of the drive unit, and 15 a hole opener being coupled to the housing of the drive unit for rotation therewith.
In an alternative development of the present invention, according to said co-pending application, the rotor of the drive unit is operatively coupled to the drill bit to rotate the drill bit in one direction, e.g. anti-clockwise, relative to the housing of the drive unit, a hole opener is coupled to the housing of the drive unit for rotation 20 therewith, and the rotor of a second drive unit is operatively coupled to the housing of the first drive unit to rotate the housing of the first drive unit in the opposite direction, e.g. clockwise, relative to the housing ofthe second drive unit.
In any of the arrangell~elll~ according to the present invention the drill bit assel.d,l~ may coll""ise part of a bottom hole as~;...l,ly for connection to the drill string, the bottom hole assembly further inç~ ling, for example, a thrust unit, one or more further hole openers, one or more stabilizers, or any other components of known kind 5 which may be incorporated in a bottom hole asse..,bly.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diag,~".-,alic side elevation of one form of drill bit assembly . according to the inventio4 shown down a borehole, and Figures 2 and 3 are similar views of altemative forms of drill bit assembly.
Rerelli"g to Figure 1: the drilling asscl-ll,ly comprises a drill bit 10 which is coupled, for example by a conventional tapered ll~n ~ed pin connector, to the output shaft or rotor 1 1 of a drive unit 12. The drive unit 12 may be an hydraulically driven positive r~i~rl~nt motor or turbine, an electric motor, or any other suitable form of 15 device for rotationally driving the drill bit.
Part way along the length of the housing of the drive unit 12 is mounted a ~ili~ 13 which acts as a fulcrum device. The ~Idbili~er may comprise a plurality of bearing elements spaced apart around the periphery of the drive unit housing.
The upper end ofthe housing ofthe drive unit 12 is directly coupled to the lower 20 end of a modulated bias unit 14, the upper end of which is connected to the drill string 15.
The bias unit 14 may be of the basic kind described in British Specification No.2259316 where a plurality of hydraulic actuators are spaced apart around the periphery of the unit and have thrust melllbel~, one of which is indicated diagrAmmAti~.Ally at 16, which may be extended to bear against the formation. A
selector control valve modulates the supply of fluid under pressure to the actuators in 5 s~ln,hr~ with rotation ofthe bias unit, and in selected angular phase relation thereto, so as to extend and retract the thrust members 16 in succ~.~ion as the bias unit rotates.
The thrust members 16 are thus each extended at a selected rotational position of the bias unit and thereby apply a constant lateral di~pl~~P.m~nt to the bias unit 14 as it rotates. As described in the above-mentioned specification, the bias unit is under the 10 control of a control unit (not shown) which may COIllyl ;se a roll stabilized instrument package conn~(ed to the drill string 15.
When the bias unit 14 is activated to initiate steering, the thrust members 16 are - ~ctuAted to extend in succes~io4 as the unit rotates, in the direction in which it is required that the borehole should deviate. Thus, as seen in Figure 1, the thrust members 15 16 extend to the right and thereby ~ ;nl~;n a con~lalll displacement of the bias unit 1 4 to the left as it is rotated by the drill string 15. This imparts a corresponding displacement to the left to the upper end of the housing of the drive unit 12 causing it to pivot anti-clockwise (as viewed in Figure 1~ about the fulcrum provided by the ~t~hili7P.r 13, thus displacing the drill bit 10 to the right. The contin~ing rotation ofthe 20 drill bit 10 by the drive unit 12 thererore causes the borehole to deviate to the right as drilling continues While the bias is being ~..A;nlh;ned the drill string 15 continues to rotate, so that friction between it and the borehole is not increased and the rate of penetration is ...h;..~ ed. When steering is no longer required the bias unit 14 is de-activated so as no longer to apply a bias to the drive unit 12.
Figure 2 shows a modified a"~u~ge"~c~ll In this case the thrust members 16 of the bias unit are located in an annular ass~"l~ly 17 which surrounds the lower end of the S drive unit 12 so as to be closer to the drill bit 10. The controlled fluid under pressure is delivered to the actuators from the control part 14 of the bias unit along conduits indicated diag,~llnldlically at 18.
In this case a stabilizer 9 is mounted on the bias unit 14, and extension of the thrust lllt;llll~l~ 16 in a co~ hlll lateral direction (to the left in Figure 2) pivots the drive 10 unit 12 and drill bit 10 anti-clockwise about the fulcrum provided by the stabilizer 9, d;i~lqr~ the d~ill bit to the right (as viewed in Figure 2) so as to cause the borehole to deviate in that direction.
Either of the drilling assenll~lies shown in each of Figures 1 and 2 may be modified to incoll~o~hle the invention of British Application No. 9521944.0, whereby 15 the drill bit 10 and drive unit 12 counter-rotate. Thus, in the case where the drill string 15 is rotated clockwise as viewed looking downhole, the drive unit 12 may be operated to rotate the drill bit 10 anti-clockwise relative to the housing of the drive unit.
British Patent Application No. 9521944.0 also describes arrangements where counter-rotation is provided in systems where the drill string itself does not rotate. The 20 present invention is equally applicable to such ~ l_nge~,e~,ls and a modification of such an a~ gelllel~l~ according to the present invention, is shown in Figure 3.
In this case the drill bit 19 is operatively coupled to the output shaft or rotor 20 21 8~332 of a first drive unit 21. The rotor 20 rotates the drill bit 19 anti-clockwise relative to the housing ofthe drive unit. Mounted on the housing ofthe first drive unit 21 is a lower hole opener 22 and an intermedi~te hole opener 23 which also serves as a fulcrum device. A~ mod~ t~l bias unit 24 is directly coupled to the upper end of the housing of 5 the drive unit 21 and is operatively coupled to the output shaft or rotor 25 of a second drive unit 26. The housing of the drive unit 26 is coupled through a thruster 27 to the drill string 28 which may be of the type formed from coiled tubing.
The second drive unit 26, which remains non-rotating with the drill string 28 and thruster 27, rotates the bias unit 24 and the housing ofthe first drive unit 21 clockwise.
10 The first drive unit 21 rotates the drill bit 19 anti-clockwise at a faster rate than the housing ofthe unit itselfis rotated clockwise by the second drive unit 26, so that the drill bit 19 rotates anti-clockwise relative to the formation. The drill bit 19 may be a PDC
drag-type drill bit, a roller cone bit, a di~mond bit or a co,l.b.nd~ion bit.
In the arrangement of Figure 3 the bias unit 24, rotated by the drive unit 26, 15 operates in similar manner to the bias unit 14 of the Figure 1 arrangement, which is rotated directly by the drill string 15. Lateral extension of each thrust member 29 of the bias unit in a selected rotational position (to the right in Figure 3) causes the bias unit and first drive unit 21 to pivot anti-clockwise about the fulcrum provided by the hole opener 23 so as to ~ pl~ce the drill bit 19 to the right and effect deviation of the 20 borehole in that direction.
The arrangement of Figure 3 thus provides both the steering advantages of the present invention with the advantages arising from counter-rotation of the drill bit and drive unit as outlined in British Patent Application No. 9521944Ø
BACKGROUND TO THE INVENTION
The invention relates to drilling assemblies for connection to a drill string for drilling holes in subsurface formations.
S As is well Icnown, in rotary drilling rotation is imparted to the drill bit by rotating from the surface a drill string to the lower end of which the drilling assembly is coupled.
The drill bit may be controlled to drill in a required directionl for example as described in British Patent Sp~-;~;f~ion No. 2259316, by cOurli~ to the drill bit a modulated bias unit which applies a lateral disp!~.cçm~nt to the drill bit in a con~t~nt direction as the bit rotates. The modulated bias unit comprises one or more hydraulic actuators the supply of fluid under plessure to which is modulated in synch~onis--~ with rotation of the unit and bit, and in selected angular phase relation thereto, the phase relation determining the direction of the bias and hence the direction in which the bit is steered.
In motor drilling the drill bit is rotated by a downhole drive unit, such as a positive disp!~ment motor or turbine. For the purposes of steering the drill bit, the drive unit may be a steerable motor having a bent housing or offset stabilizer, or the drive unit may be connected to the drill string by a device known as a bent sub, so that the bit axis is inclined to the axis of the lower end of the drill string. During unsteered drilling the drill string and drive unit are rotated so as to negate the effect of the bend, 20 and when steering is required this rotation is stopped with the inclin~tion of the bend pGillliilg in the direction in which the drill bit requires to be steered. While steering, the orientation of the bend (or offset stabilizer), referred to as the "tool-face" angle, is 21 ~8332 monitored by a directional MWD system and controlled from the surface, initially by setting the orientation of the rotary table (then stationary). The tool-face angle is also influenced, through torsional strain, by torque in the drill string. Torque is dependent on weight on bit, and short term changes in measured tool-face angle are corrected by S adjusting weight on bit. Tool-face angle and weight on bit are influenced by torque and drag due to friction between the drill string and the side of the hole. This influence makes steering difficult in long reach holes having high inclination in which much of the string weight is supported on the lower side of the hole. The extra length of the string adds to its angular and linear co...~ r~, further increasing the influences of torque and 10 drag. These difficulties are partly overcome by using extra care and by drilling slowly to minimise distulbances due to torque at the bit. Despite this, torque and drag effects do set a limit of reach beyond which steering by o~ ing becomes impracticable. These difficulties do not apply during unsteered drilling because the drill string is rotated contin-lo..~ly reducing drag and its effect on weight on bit, and also because there is then 15 no need to control tool-face angle. Thus the loss of pent~ lion rate while steering to make directional corrections increases as lateral reach is increased.
The present invention provides a downhole drilling assembly where the drill bit is rotated by a downhole drive unit, but where steering may be effected without the neces~ity of ceasing rotation of the drill string.
Acco-ding to the invention there is provided a drilling as~lllbly for drilling holes in subsurface formations, co~ lis;ng a drill bit, a drive unit in~ dir~ a housing and a rotor operatively coupled to the drill bit to rotate the drill bit relative to the housing, and a modulated bias unit coupled to rotate with the drive unit housing and apply a lateral bias thereto in s~..cllrol~ism with rotation of the housing.
The modulated bias unit may co~ -;se one or more actuators including members S which, in use, may bear against the sides of the borehole, and means for modul~ting the force and/or motion ofthe actuators in sy..cl--~l~is-ll with rotation of a component of the drilling asse..lbly, and in s~lected angular phase relation thereto, whereby the, or each, actuator is actuated over a selected rotational range of said component.
The actuators ofthe modulated bias unit may comprise hydraulic actuators, said 10 means for modulating the force and/or motion ofthe actuators comprising means for modul~ting the pressure and/or volume of fluid supplied to the actuators.
~ nple,s of hydraulic and non-hydraulic mod~ ted bias units are described in British Patent No. 2259316 and U.S. Patents Nos. 5113953 and 3743034.
The drive unit may include fulcrum means which, in use, engage the walls of the 15 borehole being drilled, the fulcrum means being located b~lweell the modulated bias unit and the drill bit whereby the lateral bias applied by the modulated bias unit causes the drive unit to pivot about the fulcrum means so as to apply to the drill bit a lateral bias in the opposite direction to the bias applied to the drive unit by the bias unit.
Alternatively, the actu~tors of the modulated bias unit may be located adjacent 20 the drill bit so as to apply a lateral bias to the drill bit in the same direction as the lateral bias applied to the drive unit.
These last-.~ ;ol1ed ~.i.. ~.. ~1~ thus permit steering ofthe drill bit while the drill string is rotating, reducing drag and avoiding the need to control motor orientation or tool-face angle by frequent monilo~i..g and ~rlj~ from the surface. Penetration rates may therefore be ...~ Ai~ed even while steering is taking place.
All;.n~...~ in ~ccor~&~ce with the invention may be used with any downhole 5 drilling asscllll~ly where the drill bit is rotated by a downhole drive unit and, in particular, it may employed in arrangcnlellls accordi,~ to our co-pending Application No.
where the drill bit and the drive unit which rotates it are counter-l oLali,~g so as to reduce the net reaction torque l, ~ ~1ed to the drill string, as well as providing other benefits as ~cr~, I cd to in that application.
Accordingly, in a drilling asse... ,bly, incorporating a modulated bias unit, in accordance with the present invention, the drill bit may carry cutters located and orientated to pc,~o.... cutting action on the formation as the drill bit rotates anti-clockwise relative thereto, the rotor of the drive unit being operatively coupled to the drill bit to rotate the drill bit anti-clockwise relative to the housing of the drive unit, and 15 a hole opener being coupled to the housing of the drive unit for rotation therewith.
In an alternative development of the present invention, according to said co-pending application, the rotor of the drive unit is operatively coupled to the drill bit to rotate the drill bit in one direction, e.g. anti-clockwise, relative to the housing of the drive unit, a hole opener is coupled to the housing of the drive unit for rotation 20 therewith, and the rotor of a second drive unit is operatively coupled to the housing of the first drive unit to rotate the housing of the first drive unit in the opposite direction, e.g. clockwise, relative to the housing ofthe second drive unit.
In any of the arrangell~elll~ according to the present invention the drill bit assel.d,l~ may coll""ise part of a bottom hole as~;...l,ly for connection to the drill string, the bottom hole assembly further inç~ ling, for example, a thrust unit, one or more further hole openers, one or more stabilizers, or any other components of known kind 5 which may be incorporated in a bottom hole asse..,bly.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diag,~".-,alic side elevation of one form of drill bit assembly . according to the inventio4 shown down a borehole, and Figures 2 and 3 are similar views of altemative forms of drill bit assembly.
Rerelli"g to Figure 1: the drilling asscl-ll,ly comprises a drill bit 10 which is coupled, for example by a conventional tapered ll~n ~ed pin connector, to the output shaft or rotor 1 1 of a drive unit 12. The drive unit 12 may be an hydraulically driven positive r~i~rl~nt motor or turbine, an electric motor, or any other suitable form of 15 device for rotationally driving the drill bit.
Part way along the length of the housing of the drive unit 12 is mounted a ~ili~ 13 which acts as a fulcrum device. The ~Idbili~er may comprise a plurality of bearing elements spaced apart around the periphery of the drive unit housing.
The upper end ofthe housing ofthe drive unit 12 is directly coupled to the lower 20 end of a modulated bias unit 14, the upper end of which is connected to the drill string 15.
The bias unit 14 may be of the basic kind described in British Specification No.2259316 where a plurality of hydraulic actuators are spaced apart around the periphery of the unit and have thrust melllbel~, one of which is indicated diagrAmmAti~.Ally at 16, which may be extended to bear against the formation. A
selector control valve modulates the supply of fluid under pressure to the actuators in 5 s~ln,hr~ with rotation ofthe bias unit, and in selected angular phase relation thereto, so as to extend and retract the thrust members 16 in succ~.~ion as the bias unit rotates.
The thrust members 16 are thus each extended at a selected rotational position of the bias unit and thereby apply a constant lateral di~pl~~P.m~nt to the bias unit 14 as it rotates. As described in the above-mentioned specification, the bias unit is under the 10 control of a control unit (not shown) which may COIllyl ;se a roll stabilized instrument package conn~(ed to the drill string 15.
When the bias unit 14 is activated to initiate steering, the thrust members 16 are - ~ctuAted to extend in succes~io4 as the unit rotates, in the direction in which it is required that the borehole should deviate. Thus, as seen in Figure 1, the thrust members 15 16 extend to the right and thereby ~ ;nl~;n a con~lalll displacement of the bias unit 1 4 to the left as it is rotated by the drill string 15. This imparts a corresponding displacement to the left to the upper end of the housing of the drive unit 12 causing it to pivot anti-clockwise (as viewed in Figure 1~ about the fulcrum provided by the ~t~hili7P.r 13, thus displacing the drill bit 10 to the right. The contin~ing rotation ofthe 20 drill bit 10 by the drive unit 12 thererore causes the borehole to deviate to the right as drilling continues While the bias is being ~..A;nlh;ned the drill string 15 continues to rotate, so that friction between it and the borehole is not increased and the rate of penetration is ...h;..~ ed. When steering is no longer required the bias unit 14 is de-activated so as no longer to apply a bias to the drive unit 12.
Figure 2 shows a modified a"~u~ge"~c~ll In this case the thrust members 16 of the bias unit are located in an annular ass~"l~ly 17 which surrounds the lower end of the S drive unit 12 so as to be closer to the drill bit 10. The controlled fluid under pressure is delivered to the actuators from the control part 14 of the bias unit along conduits indicated diag,~llnldlically at 18.
In this case a stabilizer 9 is mounted on the bias unit 14, and extension of the thrust lllt;llll~l~ 16 in a co~ hlll lateral direction (to the left in Figure 2) pivots the drive 10 unit 12 and drill bit 10 anti-clockwise about the fulcrum provided by the stabilizer 9, d;i~lqr~ the d~ill bit to the right (as viewed in Figure 2) so as to cause the borehole to deviate in that direction.
Either of the drilling assenll~lies shown in each of Figures 1 and 2 may be modified to incoll~o~hle the invention of British Application No. 9521944.0, whereby 15 the drill bit 10 and drive unit 12 counter-rotate. Thus, in the case where the drill string 15 is rotated clockwise as viewed looking downhole, the drive unit 12 may be operated to rotate the drill bit 10 anti-clockwise relative to the housing of the drive unit.
British Patent Application No. 9521944.0 also describes arrangements where counter-rotation is provided in systems where the drill string itself does not rotate. The 20 present invention is equally applicable to such ~ l_nge~,e~,ls and a modification of such an a~ gelllel~l~ according to the present invention, is shown in Figure 3.
In this case the drill bit 19 is operatively coupled to the output shaft or rotor 20 21 8~332 of a first drive unit 21. The rotor 20 rotates the drill bit 19 anti-clockwise relative to the housing ofthe drive unit. Mounted on the housing ofthe first drive unit 21 is a lower hole opener 22 and an intermedi~te hole opener 23 which also serves as a fulcrum device. A~ mod~ t~l bias unit 24 is directly coupled to the upper end of the housing of 5 the drive unit 21 and is operatively coupled to the output shaft or rotor 25 of a second drive unit 26. The housing of the drive unit 26 is coupled through a thruster 27 to the drill string 28 which may be of the type formed from coiled tubing.
The second drive unit 26, which remains non-rotating with the drill string 28 and thruster 27, rotates the bias unit 24 and the housing ofthe first drive unit 21 clockwise.
10 The first drive unit 21 rotates the drill bit 19 anti-clockwise at a faster rate than the housing ofthe unit itselfis rotated clockwise by the second drive unit 26, so that the drill bit 19 rotates anti-clockwise relative to the formation. The drill bit 19 may be a PDC
drag-type drill bit, a roller cone bit, a di~mond bit or a co,l.b.nd~ion bit.
In the arrangement of Figure 3 the bias unit 24, rotated by the drive unit 26, 15 operates in similar manner to the bias unit 14 of the Figure 1 arrangement, which is rotated directly by the drill string 15. Lateral extension of each thrust member 29 of the bias unit in a selected rotational position (to the right in Figure 3) causes the bias unit and first drive unit 21 to pivot anti-clockwise about the fulcrum provided by the hole opener 23 so as to ~ pl~ce the drill bit 19 to the right and effect deviation of the 20 borehole in that direction.
The arrangement of Figure 3 thus provides both the steering advantages of the present invention with the advantages arising from counter-rotation of the drill bit and drive unit as outlined in British Patent Application No. 9521944Ø
Claims (8)
1. A drilling assembly for drilling holes in subsurface formations, comprising a drill bit, a drive unit including a housing and a rotor operatively coupled to the drill bit to rotate the drill bit relative to the housing, and a modulated bias unit coupled to rotate with the drive unit housing and apply a lateral bias thereto in synchronism with rotation of the housing.
2. A drilling assembly according to Claim 1, wherein the modulated bias unit comprises at least one actuator including a member which, in use, bears against the sides of the borehole, and means for modulating the force and/or motion of the actuators in synchronism with rotation of a component of the drilling assembly, and in selected angular phase relation thereto, whereby the actuator is actuated over a selected rotational range of said component.
3. A drilling assembly according to Claim 2, wherein each actuator of the modulated bias unit comprises a hydraulic actuator, said means for modulating the force and/or motion of the actuator comprising means for modulating the pressure and/or volume of fluid supplied to the actuators.
4. A drilling assembly according to Claim 1, wherein the drive unit includes fulcrum means which, in use, engage the walls of the borehole being drilled, the fulcrum means being located between the modulated bias unit and the drill bit whereby the lateral bias applied by the modulated bias unit causes the drive unit to pivot about the fulcrum means so as to apply to the drill bit a lateral bias in the opposite direction to the bias applied to the drive unit by the bias unit.
5. A drilling assembly according to Claims 1, wherein each actuator of the modulated bias unit is located adjacent the drill bit so as to apply a lateral bias to the drill bit in the same direction as the lateral bias applied to the drive unit.
6. A drilling assembly according to Claim 1, wherein the drill bit carries cutters located and orientated to perform cutting action on the formation as the drill bit rotates anti-clockwise relative thereto, the rotor of the drive unit being operatively coupled to the drill bit to rotate the drill bit anti-clockwise relative to the housing of the drive unit, and a hole opener being coupled to the drive unit for rotation therewith.
7. A drilling assembly according to Claim 1, wherein the rotor of the drive unit is operatively coupled to the drill bit to rotate the drill bit in one direction relative to the housing of the drive unit, a hole opener is coupled to the housing of the drive unit for rotation therewith, and the rotor of a second drive unit is operatively coupled to the housing of the first drive unit to rotate the housing of the first drive unit in the opposite direction relative to the housing of the second drive unit.
8. A drilling assembly according to Claim 1, when comprising part of a bottom hole assembly for connection to the drill string, the bottom hole assembly further including at least one of: a thrust unit, a further hole opener, and a stabilizer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GBGB9521972.1A GB9521972D0 (en) | 1995-10-26 | 1995-10-26 | A drilling assembly for drilling holes in subsurface formations |
| GB9521972.1 | 1995-10-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2188332A1 true CA2188332A1 (en) | 1997-04-27 |
Family
ID=10782959
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002188332A Abandoned CA2188332A1 (en) | 1995-10-26 | 1996-10-21 | Drilling assembly for drilling holes in subsurface formations |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5778992A (en) |
| EP (1) | EP0770760A1 (en) |
| CA (1) | CA2188332A1 (en) |
| GB (2) | GB9521972D0 (en) |
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1996
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- 1996-10-11 EP EP96307428A patent/EP0770760A1/en not_active Withdrawn
- 1996-10-16 US US08/733,060 patent/US5778992A/en not_active Expired - Lifetime
- 1996-10-21 CA CA002188332A patent/CA2188332A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP0770760A1 (en) | 1997-05-02 |
| GB2306529A (en) | 1997-05-07 |
| GB2306529B (en) | 1999-02-10 |
| US5778992A (en) | 1998-07-14 |
| GB9521972D0 (en) | 1996-01-03 |
| GB9621206D0 (en) | 1996-11-27 |
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